Is It Safe To Keep A Portable Jump Starter In Your Car? "I Keep Mine In My Wife's Toyota RAV4 All The Time."

If you travel by air frequently, you will see warnings about airlines requiring passengers not to carry power banks in their checked-in luggage or overhead bins due to fears of lithium-sparked fires. Interestingly, an advertisement on the Rav4 World social media forum points out that a portable jump starter is a big power bank that some car owners might not consider regarding the risks of storing it in the trunk.

There is a certain amount of irony in the fact that a portable jump starter is a great roadside emergency tool to carry in your car; however, it is possible that it can also cause a roadside emergency in and of itself.

While I typically gloss over any advertisements in forums, a recent vendor-approved AutoGuide.com ad in the Rav4World forum caught my attention because I have always wondered if portable jump starters were safe in cars as they typically carry a lithium battery and are something likely to be left in the trunk and forgotten about until the need arises.

And I am not alone with these related thoughts. FronteirGeek1966 posts on the forum:

Interesting that a portable jump starter that is supposed to get you out of dead battery trouble shouldn't be stored in the car. Then it is worth what? I keep mine in my wife's RAV4 all the time, been there for years, still powers up just fine.

Which is why I have not bought one and prefer to count on my warranty and insurance provider free roadside service perks.

Portable Jump Starters

According to the AutoGuide.com ad, this is a legitimate question in need of answers:

A portable jump starter can be a lifesaver. However, like all electronic devices, portable jump starters have specific requirements for care and storage to ensure they remain functional and safe. One question that comes up is whether it's safe to keep a portable jump starter in a car when it's not in use; isn't that the point, after all?

Portable jump starters are handy devices that allow you to jump-start a dead car battery without needing another vehicle. They work by providing a burst of electrical power to your car's battery, enabling the engine to start.

Key facts about portable jump starters are:

1. They typically contain lithium-ion or lead-acid batteries, which store electrical energy.
2. They are designed to connect to your car's battery; however, all cars differ in their owner's manual instructions for safe jump starting, and you should always follow the instructions rather than connecting the positive clamp to the positive post and the negative clamp to the negative post, and hope for the best.
3. Once connected, the portable jump starter sends a high-amperage electrical current to your car's dead battery, helping the battery regain enough charge to power the starter motor, turning the engine over and starting the vehicle.
4. Some portable jump starters also have USB ports, which allow them to charge electronics such as phones, laptops, and tablets.
5. Modern jump starters have built-in safety features like reverse polarity protection (to avoid damaging the battery or the car's electrical system if the clamps are connected incorrectly) and overload protection (to prevent overcharging or short circuits).
6. After using the portable jump starter, you'll need to recharge it. Depending on the model, this can be done using a wall adapter or even through your car's 12V outlet.

Portable Jump Starters Can Be Damaged

Although a portable jump starter can quickly deliver enough power to a car's dead battery to start the engine, making it a convenient tool for emergencies, it is possible for one to become damaged while stored in your car's truck and/or while being charged, as reported this winter at an auto repair shop.

The greatest risk of a portable jump starter becoming damaged and sparking a fire emergency is due to heat exposure. However, extreme cold can damage one as well, warns the AutoGuide.com ad:

During hot summer months, the temperature inside a parked car can easily soar to 120°F (49°C) or higher, which can cause your portable jump starter's battery to overheat. Lithium-ion batteries, in particular, are susceptible to high temperatures, as heat can lead to chemical instability inside the battery, potentially causing leakage, swelling, or even combustion in rare cases.

On the flip side, freezing temperatures can reduce the overall capacity of a jump starter. Cold can cause the internal components to slow down and may prevent the jump starter from delivering the required power when you need it. In some cases, lithium-ion batteries can even freeze, leading to irreversible damage and rendering the device useless.

However, even normal day-to-day driving and environmental conditions can cause damage as well:

If a jump starter is stored loosely in the trunk, glove compartment, or under a seat, it could be subjected to unnecessary physical stress. Vibration and impacts could loosen internal connections or even cause damage to the battery cells, rendering the device ineffective or unsafe.

Exposure to moisture and humidity can also affect the performance of a jump starter… prolonged exposure to damp conditions can lead to rusting of metal components or corrosion of internal connections. This could affect the jump starter's reliability, potentially making it dangerous to use if moisture penetrates the battery or circuitry.

Safest Portable Jump Starter Precautions for Car Owners

Here are some best practices for storing your jump starter safely:

1. If possible, avoid storing your jump starter in the car altogether, especially in extreme weather. Instead, keep it in a cool, dry place in your home, garage, or office.
2. If you must store it in your car, try to keep it in an area with a relatively stable temperature. The glove compartment or under the seat may offer more protection from temperature fluctuations compared to the trunk, which can experience extreme conditions.
3. Recharge your portable jump starter every 3-6 months, even if you haven't used it. This is particularly important for lithium-ion models, which can become damaged when allowed to drain to dangerously low levels.
4. Always store your portable jump starter in a protective case, especially if you keep it in your car. A soft pouch or padded case will protect the device from physical damage caused by vibrations or impacts. Be sure that no sharp objects or heavy items are nearby that could cause it to be crushed or punctured.
5. Consider investing in models marketed as "all-weather" or "outdoor" models, which may be better suited for use in vehicles exposed to harsh conditions.

For a recent review of portable jump starters, here is one from the Project Farm YouTube channel that is a good starting point before deciding to buy a portable jump starter for your car:

Best Jump Starter I've Ever Tested!

For additional Toyota fire-related danger articles, here are two worth considering: "More than 1.8 Million Toyota RAV4 SUVs Recalled Due to Fire Risk" and "Toyota Tacoma Warning for Owners Who Camp or Park Outdoors."

Timothy Boyer is an automotive reporter based in Cincinnati who currently researches and works on restoring older vehicles with engine modifications for improved performance. He also reports on modern cars (including EVs) with a focus on DIY mechanics, buying and using tools, and other related topical automotive repair news. Follow Tim on Twitter at @TimBoyerWrites as well as on Facebook and his automotive blog "Zen and the Art of DIY Car Repair" for useful daily news and topics related to new and used cars and trucks.

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